fix typo in examples dreambooth README.md (#1073)

Update README.md

fixed typo

Author: jorahn

examples/dreambooth/README.md

@@ -185,7 +185,7 @@ accelerate launch train_dreambooth.py \
   --class_prompt="a photo of dog" \
   --resolution=512 \
   --train_batch_size=1 \
-  --use_8bit_adam
+  --use_8bit_adam \
   --gradient_checkpointing \
   --learning_rate=2e-6 \
   --lr_scheduler="constant" \
@@ -291,4 +291,4 @@ python train_dreambooth_flax.py \
   --learning_rate=2e-6 \
   --num_class_images=200 \
   --max_train_steps=800
-```
+```